As computer technology has progressed the density of electronic devices and chips within computer systems, as well as the quantity of heat produced by these devices has increased appreciably.
One of the ways employed in the past for cooling computer chips has been to blow air over the chips using a fan or blower. As the level of heat to be dissipated increases, heat sinks (such as a solid piece of a thermally conductive metal with fins) were attached to the chip and air blown across the extended surface of the heat sink. However, the use of a solid piece of metal, even aluminum or copper having a very high thermal conductivity to transfer heat, gives a significant temperature differential along the heat sink from the end connected to the heat source and the distal end with air blowing over it. If there is an insufficient transfer of heat, temperature will be high at the heat source preventing the use of high power, high density chips. In other words, the typical solid metal heat sink is too inefficient at conducting temperature away from a heat generating device to accommodate modern chip technology.
As the thermal loads of computer chips continued to increase, more effective ways to cool these chips were sought. One method developed to cool high density computer chips has been to immerse the circuit board containing the chips in a cooling liquid. Although a circulating cooling liquid has proven very effective at cooling electronic devices, a circulating fluid presents numerous disadvantages and is generally cumbersome and impractical. Liquid cooling of computer circuitry increases the cost of a computer, both its manufacturing costs and its maintenance costs. Furthermore, the plumbing and equipment necessary to circulate and cool the liquid dramatically increase the weight and complexity of the computer system.
Another method developed to cool high density computer chips has been to use a heat pipe to more efficiently transfer heat from the heat source to the air. A heat pipe is a heat transfer device consisting of a sealed metal tube with an inner lining of a wicklike capillary material and a small amount of working fluid. Heat is absorbed at one end by vaporization of the fluid and is released at the other end by condensation of the vapor. A variety of heat pipes are constructed as outlined in a brochure produced by Thermacore, Inc. (Lancaster, Pa.) for the IEPS conference in San Diego, Calif., Sep.16-18, 1991, which brochure is hereby incorporated by reference.
U.S. Pat. No. 5,095,404 (Chao patent) describes a circuit board assembly using a heat pipe to cool a high density tab automated bonding integrated circuit chip (TAB IC chip). The TAB IC chip has a small surface area (much less than 1.0 square inch), such that the circuit board assembly taught in the Chao patent requires heat to be transferred from the chip to a heat spreader, to a layer of thermal conductive material, and to a mounting pad before finally reaching a horizontally mounted heat pipe.
Today's supercomputers generate large amounts of heat that must be effectively removed from the operating chip to protect it from overheating. In order to accommodate the ever expanding need to handle increased heat dissipation, an efficient heat transfer system is needed to prevent thermal buildup within computer chips while in use.
Accordingly, it is an object of this invention to provide for a more efficient cooling means for transferring heat from a heat-generating computer chip to the surrounding air.